Polymeric tube-in-shell heat exchanger with twisted tubes

ABSTRACT

Polymeric tube-in-shell heat exchangers with twisted tubes are provided. The heat exchanger may include one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes at least one tube twisted about its length or at least one pair of tubes twisted or wound around each other. The presently disclosed polymeric tube-in-shell heat exchangers with twisted tubes may be especially suited for applications where the use of polymer tubes offers advantages, such as in the case of acid solutions, food and beverage fluids, and carbon capture applications where the use of metal heat exchangers destroy the amines used for capture.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims the benefit under 35 U.S.C. § 119(e) of U.S. Patent Application Ser. No. 63/262,403, entitled “POLYMERIC TUBE-IN-SHELL HEAT EXCHANGER WITH TWISTED TUBES,” filed on Oct. 12, 2021, which is incorporated herein by reference in its entirety.

FIELD

The present disclosure is broadly concerned with tube bundle heat exchangers, particularly, twisted tube heat exchangers.

BACKGROUND

Tube bundle heat exchangers are used in many applications and have been extensively used in automotive applications. Such heat exchangers typically include a bundle of spaced, parallel tubes enclosed in a housing or shell. A first heat exchange fluid flows through the tubes, while a second heat exchange fluid flows through the housing and passes through the interstitial spaces between the outer surfaces of the tubes.

In a typical construction of a tube bundle heat exchanger, parallel tubes of circular cross-sections are retained in place at their ends by perforated header plates, also known as tube sheets. In addition to retaining the tubes, the header plates also provide a seal to prevent flow communication between the tube interiors and the interior of the housing.

BRIEF SUMMARY

In one aspect, a polymeric tube-in-shell heat exchanger with twisted tubes is provided. The heat exchanger may include one or more polymeric tube bundles. The at least one of the one or more polymeric tube bundles includes one or more sets of two or more tubes twisted or wound around one or more tubes, each tube including a tubular wall and a passage configured for a first fluid to flow through, the heat exchanger configured for a second fluid to pass through space between the twisted tubes.

In some examples, which may be combined with each of the disclosed examples, the one or more sets of two or more tubes have a fixed length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a plurality of pairs of tubes twisted or wound around each other.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a plurality of triplets of tubes or multiple numbers of tubes twisted or wound around each other.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a plurality of non-circular tubes, each tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include an oval/elliptical tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a peanut-shaped twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a polygon twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a petal twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a lobed twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the two or more polymeric tubes include one or more external ribs extending outward from an outer surface of the two or more tubes, each tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the two or more tubes include one or more internal channels or internal ribs extending outward or inward from an inner surface of the one or more tubes, each tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the heat exchanger also includes a housing disposed outside the one or more polymeric tube bundles.

In some examples, which may be combined with each of the disclosed examples, the heat exchanger also includes an outer wrap disposed around the one or more polymeric tube bundles, the outer wrap configured to tighten the one or more polymeric tube bundles to enable tube configurations to provide uniform spacing between tubes and/or reduce space between the housing and the one or more polymeric tube bundles.

In another aspect, a polymeric tube-in-shell heat exchanger with twisted tubes is provided. The heat exchanger may include one or more polymeric tube bundles. At least one of the one or more polymeric tube bundles include a plurality of polymeric tubes. Each tube includes a tubular wall and a passage configured for a first fluid to flow through. The heat exchanger is configured for a second fluid to pass through space between the twisted tubes. At least one of the plurality of polymeric tubes includes one or more ribs extending from the tubular wall twisted about its length.

In some examples, which may be combined with each of the disclosed examples, the plurality of polymeric tubes has a fixed length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a plurality of non-circular tubes, each tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include an oval or elliptical tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a peanut-shaped twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a polygon twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a petal twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric tube bundles include a lobed twisted tube twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, at least one of the two or more tubes includes one or more internal channels or internal ribs extending outward or inward from an inner surface of the one or more tubes twisted about its respective length.

In some examples, which may be combined with each of the disclosed examples, the one or more external ribs extend outward from an outer surface of the tubular wall.

In some examples, which may be combined with each of the disclosed examples, the one or more ribs extend inward from an inner surface of the tubular wall.

In some examples, which may be combined with each of the disclosed examples, the heat exchanger also includes a housing disposed outside the one or more polymeric tube bundles.

In some examples, which may be combined with each of the disclosed examples, the heat exchanger also includes an outer wrap disposed around the one or more polymeric tube bundles, the outer wrap configured to tighten the one or more polymeric tube bundles to enable tube configurations to provide uniform spacing between tubes and/or reduce space between the housing and the one or more polymeric tube bundles.

In a further aspect, a polymeric tube-in-tube exchanger with tubes is provided. The heat exchanger includes one or more polymeric tube bundles, wherein at least one of the one or more polymeric tube bundles includes one or more polymeric dual-tube structures, each polymeric dual-tube structure including an inner tube, an outer tube, a plurality of ribs extending from an inner surface of the outer tube to an outer surface of the inner tube, the plurality of ribs being twisted along a longitudinal axis of the polymeric dual-tube structure.

In some examples, which may be combined with each of the disclosed examples, the outer tube of the polymeric dual-tube structure is straight along its respective length.

In some examples, which may be combined with each of the disclosed examples, the inner tube includes a first tubular wall and a passage configured for a first fluid to pass through, and the outer tube includes a second tubular wall. Space between an inner surface of the second tubular wall of the outer tube and an outer surface of the first tubular wall of the inner tube is configured for a second fluid to pass through.

In some examples, which may be combined with each of the disclosed examples, the one or more polymeric dual-tube structures have a fixed length.

In some examples, which may be combined with each of the disclosed examples, the heat exchanger also includes a housing disposed outside the one or more polymeric tube bundles.

In some examples, which may be combined with each of the disclosed examples, the heat exchanger also includes an outer wrap disposed around the one or more polymeric tube bundles, the outer wrap configured to tighten the one or more polymeric tube bundles to enable tube configurations to provide uniform spacing between tubes and/or reduce space between the housing and the one or more polymeric tube bundles.

In some examples, which may be combined with each of the disclosed examples, a method is provided for fabricating the one or more polymeric tube bundle. The method may include forming polymeric tubes by extrusion from a polymer. The method may also include twisting one or more polymeric tubes to form a twisted tube or a subset of two or more twisted tubes. The method may also include forming a bundle of twisted tubes from the twisted tube or the subset of two or more twisted tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the advantages and features of the disclosure can be obtained, reference is made to embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 depicts a diagrammatic view of the flow pattern of a conventional tube and shell heat exchanger, according to an exemplary embodiment of the present disclosure;

FIG. 2A depicts a graphic representation of a conventional twisted tube metal heat exchanger, according to an exemplary embodiment of the present disclosure;

FIG. 2B depicts an enlarged view of the conventional twisted tube metal heat exchanger of FIG. 2A, according to an exemplary embodiment of the present disclosure;

FIG. 3 depicts a perspective view of a twisted pair heat exchanger bundle, according to an exemplary embodiment of the present disclosure;

FIG. 4 depicts a perspective view of an oval/elliptic tube, according to an exemplary embodiment of the present disclosure;

FIG. 5 depicts a perspective view of a peanut-shaped twisted tube, according to an exemplary embodiment of the present disclosure;

FIG. 6 depicts a perspective view of a tri-polygon twisted tube, according to an exemplary embodiment of the present disclosure;

FIG. 7 depicts a perspective view of a petal twisted tube, according to an exemplary embodiment of the present disclosure;

FIG. 8 depicts a perspective view of a five-lobed twisted tube, according to an exemplary embodiment of the present disclosure;

FIG. 9 depicts a perspective view of tubes with twisted fins/ribs, according to an exemplary embodiment of the present disclosure;

FIG. 10 depicts a perspective view of a bundle of five-lobed twisted tubes, according to an exemplary embodiment of the present disclosure;

FIG. 11 depicts a perspective view of a bundle of tubes with twisted ribs, according to an exemplary embodiment of the present disclosure;

FIG. 12 illustrates a cross-section view of an outer wrap applied to a bundle of tubes inside a housing according to an exemplary embodiment of the present disclosure;

FIG. 13 illustrates a cross-section view of an outer wrap applied to a bundle of tubes with ribs inside a housing according to an exemplary embodiment of the present disclosure;

FIG. 14 illustrates a perspective view of a tube having rifling inside the tube with internal channels according to an exemplary embodiment of the present disclosure;

FIG. 15 illustrates a perspective view of a tube having rifling inside the tube with internal ribs according to an exemplary embodiment of the present disclosure;

FIG. 16A illustrates a perspective view of tube-in-tube configuration according to an exemplary embodiment of the present disclosure;

FIG. 16B illustrates an end cross-sectional view of tube-in-tube configuration according to an exemplary embodiment of the present disclosure;

FIG. 17A is a perspective view of a polymeric tube-in-shell heat exchanger according to an exemplary embodiment of the present disclosure;

FIG. 17B is a side sectional view of the polymeric tube-in-shell heat exchanger of FIG. 17A according to an exemplary embodiment of the present disclosure;

FIG. 17C is an end view of the polymeric tube-in-shell heat exchanger of FIG. 17A according to an exemplary embodiment of the present disclosure; and

FIG. 17D is an enlarged side sectional view of a portion of the polymeric tube-in-shell heat exchanger of FIG. 17B according to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 depicts a diagrammatic view of the flow pattern of a conventional tube and shell heat exchanger, according to an exemplary embodiment of the present disclosure. In the tube and shell heat exchanger 100, a first fluid 104 from tube inlet 108A passes inside the tubes 102A-D and exits from tube outlet 108B, while a second fluid 106 from shell inlet 110A passes in shell 103 around and along tubes 102 and exit from shell outlet 110B. The first fluid 104 is also referred to as an internal fluid that flows inside tubes 102A-D, while the second fluid is also referred to as an external fluid that flows outside tubes 102A-D. The shell inlet 110A is positioned near tube outlet 108B on a first end 112A, while tube inlet 108A is positioned near shell outlet 110B on a second end 112B opposite to the first end 112A. On the shell-side of the heat exchanger, the second fluid 106 passes along the tubes 102 and the bundle of tubes can provide a flow passage along a pathway as pointed by arrow 113 for the second fluid 106 to enter/leave the bundle of tubes 102 from/to the radial direction 107. In this manner, the bundle of tubes 102A-D guides the external flow of the second fluid 106 next to tubes 102A-D and reduces bypassing. Baffles 112 are used as additional supports for tubes 102A-D. The baffles 112 also help improve the distribution of fluid flow within the shell. The heat exchanger 100 may also include tube sheets or perforated header plates 114 at the ends of the tubes 102A-D are used for retaining the parallel tubes 102A-D of circular cross-sections in place at their ends.

The tube and shell heat exchanger 100 is good for high temperatures and high pressure, but the large spacing between tubes 102A-D causes a lot of flow bypassing and poor flow distribution which makes the tube and shell heat exchanger 100 have low effectiveness.

FIG. 2A depicts a graphic representation of a conventional twisted tube metal heat exchanger, according to an exemplary embodiment of the present disclosure. A twisted tube heat exchanger 200 includes multiple twisted tubes 202, which are enclosed inside enclosure 204.

FIG. 2B depicts an enlarged view of the conventional twisted tube metal heat exchanger of FIG. 2A, according to an exemplary embodiment of the present disclosure. As shown in FIG. 2B, a single metal tube 202 is twisted to have a wavy pattern along its length. The wavy pattern includes curves around an axis perpendicular to a longitudinal axis of tube 202. The twisted tube metal heat exchanger 200 eliminates baffles and damaging tube vibration. The uniquely shaped tubes are arranged on a triangular pattern that provides adjacent support as fluid swirls freely alongside. Gaps between tube 202 make it easy to clean on the shell-side.

Conventional metal heat exchangers have several issues. First, conventional metal heat exchangers may destroy the amines used for carbon capture applications. Additional applications include all waste heat applications where the metal heat exchangers are cost-prohibitive to provide a payback, as well as for fluid streams where there is differing viscosity, such as water or oil heaters. Other applications include food and beverage applications as well as acid solution applications, where the metal heat exchanges have issues with chemical resistance.

To solve the problems of the conventional twisted tube metal heat exchanger, the present disclosure provides a polymeric tube-in-shell heat exchanger with twisted tubes. A non-limiting example of this aspect is shown in FIG. 3 . Examples of non-round tubes are provided in FIGS. 4-11 .

FIG. 3 depicts a perspective view of a twisted pair heat exchanger bundle, according to an exemplary embodiment of the present disclosure. As illustrated, a twisted pair heat exchanger bundle 300 includes multiple pairs of tubes 302A and 302B, e.g., seven twisted pairs of tubes. Each pair of tubes 302A and 302B are twisted around a longitudinal axis L along its length. Each twisted pair of tubes are in contact with its neighboring twisted pair of tubes. Each tube may have a circular cross-section 304.

Pairs of circular tubes 302A and 302B provide support and allow flow passage for fluids to enter and/or leave the bundle from the axial or the radial direction. The open space between the pairs of tubes can channel the external fluid along the length of the tubes for effective heat exchange. Additionally, twisted tube pairs can generate flow direction changes along the flow path which enhances heat exchange by creating additional mixing and turbulence in the external fluid outside the tubes. The viscosity of the external fluids may affect the heat exchange. Also, the tubes may have small diameters to increase the heat exchange surface and to improve heat transfer at the surface of the tubes. Also, the fluid input and output locations can be selected to provide either co-current or counter-current flow.

It will be appreciated by those skilled in the art that the number of twisted pairs of tubes may vary in a heat exchanger bundle.

Fluids can flow into the twisted tubes from the tube end and deliver more efficient and reliable performance than the conventional shell and tube heat exchangers 100 and 200. The bundle construction in the twisted tube heat exchanger 300 can increase heat transfer and reduce pressure drops while increasing heat transfer surface area and eliminating damaging vibration. Dead spots may be eliminated. The dead spots are where fouling can accumulate and reduce effective heat transfer surface area. Fouling is the accumulation of unwanted material on solid surfaces. Also, the tubes can be configured so that the tube size and inter-tube spacing can be tailored to specific applications to control the pressure drops for the fluids both inside and outside the tubes.

According to a first aspect of the present disclosure, a polymeric tube-in-shell heat exchanger with twisted tubes is provided. The heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes at least one tube twisted about its length or at least one pair of tubes twisted or wound around each other.

According to a second aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles is made with pairs or other multiple groups of tubes wound around each other.

According to a third aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of non-circular tubes twisted about their respective lengths. In such instances, the use of non-circular tubes twisted around their lengths provides similar capabilities as the twisted pair embodiment but without having a pair, thus simplifying the assembly process. The shell-side fluid or external fluid outside the tube can be arranged to have either axial or radial access to enter and leave the bundle. Voids between the twisted tubes allow passages along the tubes guiding the shell-side fluid next to the tubes that contain an internal fluid for effective heat exchange between the shell-side fluid and the internal fluid inside the tube. Additionally, twisted non-circular tubes act as supports and baffles. They create additional turbulence thereby enhancing heat transfer. Having no additional supports, baffles, etc. yields tight packaging of the heat exchanger, compact size, and low weight, and reduces the overall cost of the unit. Examples of non-round tubes are provided in FIGS. 4-11 .

FIG. 4 depicts a perspective view of an oval or elliptic twisted tube, according to an exemplary embodiment of the present disclosure. As illustrated, a twisted tube 400 may have an oval or elliptic cross-section 404. The tube 400 is twisted around its longitudinal axis L along its length. The twisted tube 400 has an outer surface 402 including a twist mark 406, which is a compression into a cylindrical surface of an untwisted tube.

FIG. 5 depicts a perspective view of a peanut-shaped twisted tube, according to an exemplary embodiment of the present disclosure. As illustrated, a peanut twisted tube 500 includes first and second twisted tube sections 502A and 502B, which are connected along its longitudinal axis L. The peanut twisted tube 500 has a peanut-shaped cross-section 504 which varies along the longitudinal axis L. Also, tube 500 has an outer surface 506 formed by a portion of the first twisted tube section 502A and a portion of the second twisted tube section 502B. Inside outer surface 506 is a hollow portion 505 to allow fluids to pass through.

FIG. 6 depicts a perspective view of a tri-polygon twisted tube, according to an exemplary embodiment of the present disclosure. A tri-polygon tube 600 may have a tri-polygon cross-section 604 which varies along its longitudinal axis L. The tri-polygon tube 600 is twisted around its longitudinal axis L along its length. The twisted tube 600 has an outer surface 602 including a twist mark 606, which is a compression into a tri-polygon surface of an untwisted tube.

It will be appreciated by those skilled in the art that the twisted tube may have a cross-section of any polygon.

FIG. 7 depicts a perspective view of a petal twisted tube, according to an exemplary embodiment of the present disclosure. A petal-twisted tube 700 includes four tubes 702A-D that have their outer portions connected and inner portions removed to form a single tube. The petal-twisted tube 700 is twisted around its longitudinal axis L along its length. The petal-twisted tube 700 includes an outer shell 706 having a petal-like cross-section that varies along the longitudinal axis L. Inside shell 706 is a hollow portion 704 to allow fluids to pass through.

FIG. 8 depicts a perspective view of a five-lobed twisted tube, according to an exemplary embodiment of the present disclosure. A five-lobed twisted tube 800 includes five half-tubes 802A-E that have their outer portions connected and inner portions removed to form a single tube. The five-lobed twisted tube 800 is twisted around its longitudinal axis L along its length. The five-lobed twisted tube 800 includes a shell 806 having a five-lobed cross-section 804 that varies along the longitudinal axis L. Inside shell 806 is a hollow portion 805 which allows fluids to pass through.

FIG. 9 depicts a perspective view of tubes with twisted fins/ribs, according to an exemplary embodiment of the present disclosure. As illustrated, a first twisted tube 902A is twisted around its longitudinal axis L along its length. The first twisted tube 902A includes three ribs or fins 906A-C that extend outward beyond a circular shell 908 and increase the surface area for heat exchange. The surface area for the heat exchange increases with the height of the ribs or fins. The ribs 906A-C may be equally spaced along a circular cross-section 904. Also, a second twisted tube 902B is twisted around its longitudinal axis L along its length. The second twisted tube 902B includes one rib 906D. Further, a third twisted tube 902C is twisted around its longitudinal axis L along its length. The third twisted tube 902C includes two ribs 906E-F that are opposite to each other from the center of the circular cross-section 904. The spacing 914 between the fins or ribs 902 along a longitudinal axis may vary for different twisted tubes. In addition to providing additional heat transfer surface area, the twisted ribs enable the tubes to be self-supporting within the tube bundle and to control the inter-tube spacing for improved flow distribution of the external fluid passing through the shell 908 along the outsides of the tubes, and also improving the heat transfer.

FIG. 10 depicts a perspective view of a bundle of five-lobed twisted tubes, according to an exemplary embodiment of the present disclosure. A bundle of twisted tubes 1000 includes multiple five-lobed twisted tubes 800. Each five-lobed twisted tube 800 contacts its neighboring five-lobed twisted tube 800.

FIG. 11 depicts a perspective view of a bundle of tubes with twisted ribs, according to an exemplary embodiment of the present disclosure. A bundle of twisted tubes 1100 includes multiple tubes with twisted ribs. Each tube 900 with ribs contacts its neighboring tube 900 with ribs. The use of external ribs or fins helps improve heat transfer by providing additional surface area. In some variations, the tubes can have internal ribs or fins, which also help improve heat transfer by providing additional surface area. In addition to providing additional heat transfer surface area, the twisted ribs enable the tubes to be self-supporting within the tube bundle and to control the inter-tube spacing for improved flow distribution of the external fluid passing through the shell 908 along the outsides of the tubes, and also improving the heat transfer.

The shapes and sizes of the tubes can be customized to control the cross-sectional area ratios suitable for fluids having various viscosities and thermal conductivities to improve heat exchange and control pressure drops.

The bundle of twisted tubes also provides the ability to control the interstitial space uniformity to generate good flow distribution and bypass control.

FIG. 12 illustrates a cross-section view of an outer wrap applied to a bundle of tubes inside a housing according to an exemplary embodiment of the present disclosure. A polymeric heat exchanger 1200 includes a housing 1202 and an outer wrap 1204 wrapped around the bundle of tubes 1206 to tighten the bundles. The bundle of tubes 1206 with the outer wrap is placed within housing 1202. The outer wrap 1204 provides compression for the tube bundle to make the tubes contact each other and thus helps eliminate the bypass path along the inside surface of the shell. The outer wrap also helps control the bypass of the flow between the tubes within the bundle. Due to the dimension variations of the pipes, there may be space between the bundle of the tubes and housing 1202. The outer wrap helps fill the space between the outer surface of the bundle of tubes 1206 and housing 1202 and thus has control of the bypass of the flow. Although most tubes 1206 may contact each other, there may still have space 1208 between tubes 1206.

FIG. 13 illustrates a cross-section view of an outer wrap applied to a bundle of tubes with ribs inside a housing according to an exemplary embodiment of the present disclosure. A polymeric heat exchanger 1300 includes a housing 1302 and an outer wrap 1304 wrapped around the bundle of tubes 1306 with ribs 1308 to tighten the bundles. The bundle of tubes 1306 with the outer wrap 1304 is placed within housing 1302. The outer wrap 1304 provides compression for the tube bundle to make the tubes 1306 contact each other and thus helps eliminate the by-pass path along the inside surface of the shell. Although most tubes 1306 may contact each other, there may still have space 1310 between tubes 1306.

In some variations, the outer wrap may be formed of a stretchable woven fabric.

In some variations, the housing may be a rigid plastic pipe, such as PVC or polypropylene.

In some variations, the housing may be a glass fiber-reinforced plastic pipe.

In some variations, the tubes may have ribs outside.

FIG. 14 illustrates a perspective view of a tube having rifling inside the tube with internal channels according to an exemplary embodiment of the present disclosure. As shown, a polymeric tube 1400 includes three channels 1402 extending outward from an inner surface 1406 of a tubular wall 1404 twisted about its respective length along a longitudinal axis L. The number of channels may vary. The internal channels 1402 look like a spiral curve when viewed from an end, as illustrated by the dashed lines. The internal channels 1402 can improve surface exposure and/or turbulence for improved heat exchange.

FIG. 15 illustrates a perspective view of a tube having rifling inside the tube with internal ribs according to an exemplary embodiment of the present disclosure. As shown, a polymeric tube 1500 includes three internal ribs 1502 extending outward from an inner surface 1506 of a tubular wall 1504 twisted about its respective length along a longitudinal axis L. The number of ribs may vary. The internal ribs 1502 look like a spiral curve when viewed from an end, as illustrated by the dashed lines. The internal ribs 1502 can improve surface exposure and/or turbulence for improved heat exchange.

FIG. 16A illustrates a perspective view of tube-in-tube configuration according to an exemplary embodiment of the present disclosure. FIG. 16B illustrates an end cross-sectional view of tube-in-tube configuration according to an exemplary embodiment of the present disclosure. As illustrated, a polymeric dual-tube structure 1600 includes an outer tube 1602 and an inner tube 1604. The dual-tube structure 1600 also includes ribs 1606 between the outer tube 1602 and inner tube 1604 to support and control the location of the inner tube. The ribs 1606 extend from an inner surface 1608 of the outer tube 1602 to an outer surface 1610 of the inner tube 1604. For example, the dimension of the ribs controls the space between the inner tube and the outer tube. The ribs 1606 of the dual-tube structure are twisted about its respective length along a longitudinal axis L. The dual-tube structure 1600 allows having an annular flow of a first fluid in space 1612 between the inner tube and the outer tube. The dual-tube structure 1600 allows having a flow of a second fluid inside a hollow portion 1614 of the inner tube. The surfaces (e.g., outer surface 1609 and inner surface 1608 of the outer tube 1602, inner surface 1611 and outer surface 1610 of the inner tube 1604) and ribs 1606 of the tube 1600 can be either straight or twisted. The dual-tube structure 1600 can for a tube bundle in which the dual-tube structure 1600 contact each other.

FIG. 17A is a perspective view of a polymeric tube-in-shell heat exchanger according to an exemplary embodiment of the present disclosure. FIG. 17B is a side sectional view of the polymeric tube-in-shell heat exchanger of FIG. 17A according to an exemplary embodiment of the present disclosure. FIG. 17C is an end view of the polymeric tube-in-shell heat exchanger of FIG. 17A according to an exemplary embodiment of the present disclosure. FIG. 17D is an enlarged side sectional view of a portion of the polymeric tube-in-shell heat exchanger of FIG. 17B according to an exemplary embodiment of the present disclosure. As illustrated, a polymeric tube-in-shell heat exchanger 1700 includes a housing 1712, an inlet housing 1702A and an outlet housing 1702B for a shell fluid 1703 to flow into the housing 1712 and between tubes 1708. The polymeric tube-in-shell heat exchanger 1700 also includes an inlet 1704A and an outlet 1704B for a tube fluid 1706 to flow through the tubes 1708. The outlet housing 1702B for the shell-fluid 1703 is close to the inlet 1704A for the tube fluid 1706, while the inlet housing 1702A for the shell-fluid 1703 is close to the outlet 1704B for the tube fluid 1706, such that the shell-fluid 1703 is counter flow to the tube fluid 1706 to increase efficiency of the heat exchange. Also, the tubes 1708 contact each other. The tubes or ribs inside the tubes can be twisted as illustrated in FIGS. 3-15 . The shell-fluid 1703 can fill the space between the tubes.

The polymeric tube-in-shell heat exchanger 1700 also includes an outer wrap layer 1710, which includes a potting material, such as epoxy, polyurethane or any other appropriate material that fills the space around the tube 1708 and seals on the tube 1708 and inner wall of the housing 1712 The inlet 1704A includes a connection 1714 that is configured to fit outside the housing 1712. Similarly, the outlet 1704B includes a connection 1714 that is configured to fit outside the housing 1712. The inlet housing 1702A and the outlet ousing 1702B also include a connection 1716 that is configured to fit outside the housing 1712.

Methods of Fabricating Polymeric Twisted Tubes

Polymeric or plastic tubes can be made by extrusion. The polymeric tubes may be made to have ribs or fins Then, the polymeric tubes can be twisted.

In some variations, the polymeric tubes may be twisted right after the extrusion when the polymeric tubes are still soft and easy to be twisted.

In some variations, the polymeric tubes may be provided by a supplier. The polymeric tubes may be heated up to be soft enough without losing their shape for twisting.

In some variations, the polymeric tubes may be extruded without twisting to have the shapes as illustrated in FIGS. 3-15 and 16A-B. The twist is provided by extrusion without any subsequent twisting process.

In some variations, two or more polymeric tubes are twisted over each other along their lengths. Then, the twisted pairs or other multiples of polymeric tubes can be bundled together.

In some variations, a single polymeric tube with fins or ribs can be twisted along its length. Then, the twisted polymeric tubes can be bundled together.

Experiments on a Twisted Tube Heat Exchanger

A twisted tube plastic heat exchanger including 60 twisted tubes was assembled from polyether ether ketone (PEEK) tubes. The PEEK tubes had an outer diameter of 1.5 mm and an inner diameter of 1.3 mm with spiral ribs, as shown in FIG. 9 . Each pair of 60 tubes was twisted 55 times around each other. Water was fed from the tank to the heat exchanger. Cold water was fed to the heat exchanger in an opposite direction from hot water to have a counterflow in the heat exchanger. Pressure drop was measured with vertical tubes. Temperatures were measured by using thermocouples.

At a flow rate of 210 mL/min, the cold side (or shell-side) produced a pressure drop of 0.08 psi, and the hot side (tubes) produced a pressure drop of 0.21 psi. The cold side water was heated from 16° C. to 76° C. The hot water was cooled from 79° C. down to 21° C. Heat transfer coefficients were calculated for both sides of the heat exchange.

Table 1 lists the comparison of the disclosed polymeric densely-packed tube-in-shell heat exchanger and the metal tube-and-shell heat exchanger. As shown in Table 1, the disclosed polymeric densely-packed tube-in-shell heat exchanger is more effective than the metal tube and shell heat exchanger, e.g., having about 80% effectiveness.

Also, for typical tube and shell heat exchangers with cross-flow, such as the metal tube and shell heat exchanger, the hot shell fluid is much hotter than the cold fluid. The flow rate is also higher, so temperature change is lower than the cold fluid. This results in no “cross-over” of temperature, i.e., the hot fluid outlet temperature is higher than the cold fluid outlet temperature. The effect of this is a high logarithmic mean temperature difference (LMTD). For heat recovery heat exchangers, it is desirable to recover as much of the heat as possible and keep the LMTD minimal, which allows the cold fluid outlet temperature to be higher than the hot fluid outlet temperature. The disclosed polymeric heat exchanger with counterflow can accomplish the low LMTD.

Also, the disclosed polymeric densely-packed tube-in-shell heat exchanger has a surface area packing density significantly higher than the metal tube and shell heat exchanger and is lower cost than the metal tube and shell heat exchanger.

TABLE 1 Comparison of Two Heat Exchangers Metal Tube Polymeric Densely Packed and Shell Tube-in-Shell heat exchanger heat Prototype Target exchanger Test Data Values Flow Pattern Cross- Counter- Counter- Flow flow flow Effectiveness Low 78% 80%+ U-Factor (water to water) 230-400 230 200-400 LMTD (° C.) High 12  5-10 Surface Area Packing  50-500 1125 1000+ Density (m²/m³) Cost Low Lowest Lowest

The tubular shape of the tubes provides better structural strength as compared to sheet/plate heat exchangers. Additionally, tubes are economical to make by extrusion. Polymeric tubes have thin walls to obtain low thermal resistance. Further, the small diameter and low hydraulic diameters on both sides, i.e., the shell-side (outside the tube) and tube-side (inside the tube), provide high heat transfer at the surface of the tubes. The use of smooth polymeric tubes can have low-pressure losses, low fouling, and easy cleaning of the exchanger. Additionally, the use of polymeric materials provides great chemical resistance.

Also, the twisted tube bundle has no additional supports, such as baffles, among others, such that the twisted tube bundle yields tight packaging of the heat exchanger, compact size, low weight and reduces overall cost.

According to a fourth aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of oval or elliptical tubes twisted about their respective lengths.

According to a fifth aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of peanut-shaped twisted tubes twisted about their respective lengths.

According to a sixth aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of tri-polygon or other polygon twisted tubes twisted about their respective lengths.

According to a seventh aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of petal twisted tubes twisted about their respective lengths.

According to an eighth aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of five-lobe twisted tubes twisted about their respective lengths.

According to a ninth aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of tubes with twisted fins/ribs.

According to a tenth aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of five-lobe twisted tubes.

According to an eleventh aspect of the present disclosure, the heat exchanger includes one or more polymeric tube bundles, wherein each of the one or more polymeric tube bundles includes a plurality of twisted rib tubes.

The presently disclosed polymeric tube-in-shell heat exchangers with twisted tubes may be especially suited for carbon capture applications since metal heat exchangers destroy the amines used for carbon capture. Additional applications include all waste heat applications where metal heat exchangers are cost-prohibitive to provide a payback, as well as for fluid streams where there is differing viscosity, such as water/oil heaters. Other applications include food and beverage applications as well as acid solution applications where the use of polymer tubes offers benefits over metal heat exchangers. 

1. A polymeric tube-in-shell heat exchanger with twisted tubes, the heat exchanger comprising: one or more polymeric tube bundles, wherein at least one of the one or more polymeric tube bundles comprises one or more sets of two or more tubes twisted or wound around one or more tubes, each tube comprising a tubular wall and a passage configured for a first fluid to flow through, the heat exchanger configured for a second fluid to pass through space between the twisted tubes.
 2. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more sets of two or more tubes have a fixed length.
 3. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise a plurality of pairs of tubes twisted or wound around each other.
 4. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise a plurality of triplets of tubes or multiple numbers of tubes twisted or wound around each other.
 5. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise a plurality of non-circular tubes, each tube twisted about its respective length.
 6. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise an elliptical tube twisted about its respective length.
 7. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise a peanut-shaped twisted tube twisted about its respective length.
 8. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise a polygon twisted tube twisted about its respective length.
 9. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise a petal twisted tube twisted about its respective length.
 10. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the one or more polymeric tube bundles comprise a lobed twisted tube twisted about its respective length.
 11. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the two or more polymeric tubes comprise one or more external ribs extending outward from an outer surface of the two or more tubes twisted, each tube about its respective length.
 12. A polymeric tube-in-shell heat exchanger according to claim 1, wherein the two or more tubes comprise one or more internal channels or internal ribs extending outward or inward from an inner surface of the one or more tubes twisted about its respective length.
 13. A polymeric tube-in-shell heat exchanger according to claim 1, further comprising a housing disposed outside the one or more polymeric tube bundles.
 14. A polymeric tube-in-shell heat exchanger according to claim 1, further comprising an outer wrap disposed around the one or more polymeric tube bundles, the outer wrap configured to tighten the one or more polymeric tube bundles to enable tube configurations to provide uniform spacing between tubes and/or reduce space between the housing and the one or more polymeric tube bundles.
 15. A polymeric tube-in-shell heat exchanger with twisted tubes, the heat exchanger comprising: one or more polymeric tube bundles, at least one of the one or more polymeric tube bundles comprising a plurality of polymeric tubes, each tube comprising a tubular wall and a passage configured for a first fluid to flow through, the heat exchanger configured for a second fluid to pass through space between the twisted tubes, wherein at least one of the plurality of polymeric tubes comprises one or more ribs extending from the tubular wall twisted about its length.
 16. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the plurality of polymeric tubes has a fixed length.
 17. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more polymeric tube bundles comprise a plurality of non-circular tubes, each tube twisted about its respective length.
 18. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more polymeric tube bundles comprise an elliptical tube twisted about its respective length.
 19. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more polymeric tube bundles comprise a peanut-shaped twisted tube twisted about its respective length.
 20. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more polymeric tube bundles comprise a polygon twisted tube twisted about its respective length.
 21. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more polymeric tube bundles comprise a petal twisted tube twisted about its respective length.
 22. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more polymeric tube bundles comprise a lobed twisted tube twisted about its respective length.
 23. A polymeric tube-in-shell heat exchanger according to claim 15, wherein at least one of the two or more tubes comprises one or more internal channels or internal ribs extending outward or inward from an inner surface of the one or more tubes twisted about its respective length.
 24. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more external ribs extend outward from an outer surface of the tubular wall.
 25. A polymeric tube-in-shell heat exchanger according to claim 15, wherein the one or more ribs extend inward from an inner surface of the tubular wall.
 26. A polymeric tube-in-shell heat exchanger according to claim 15, further comprising a housing disposed outside the one or more polymeric tube bundles.
 27. A polymeric tube-in-shell heat exchanger according to claim 15, further comprising an outer wrap disposed around the one or more polymeric tube bundles, the outer wrap configured to tighten the one or more polymeric tube bundles to enable tube configurations to provide uniform spacing between tubes and/or reduce space between the housing and the one or more polymeric tube bundles.
 28. A polymeric tube-in-tube exchanger with tubes, the heat exchanger comprising: one or more polymeric tube bundles, wherein at least one of the one or more polymeric tube bundles comprises one or more polymeric dual-tube structures, each polymeric dual-tube structure comprising an inner tube, an outer tube, a plurality of ribs extending from an inner surface of the outer tube to an outer surface of the inner tube, the plurality of ribs being twisted along a longitudinal axis of the polymeric dual-tube structure.
 29. A polymeric tube-in-shell heat exchanger according to claim 28, wherein the outer tube of the polymeric dual-tube structure is straight along its respective length.
 30. A polymeric tube-in-shell heat exchanger according to claim 28, wherein the inner tube comprises a first tubular wall and a passage configured for a first fluid to pass through, and the outer tube comprising a second tubular wall, space between an inner surface of the second tubular wall of the outer tube and an outer surface of the first tubular wall of the inner tube configured for a second fluid to pass through.
 31. A polymeric tube-in-shell heat exchanger according to claim 28, wherein the one or more polymeric dual-tube structures have a fixed length.
 32. A polymeric tube-in-shell heat exchanger according to claim 28, further comprising a housing disposed outside the one or more polymeric tube bundles.
 33. A polymeric tube-in-shell heat exchanger according to claim 28, further comprising an outer wrap disposed around the one or more polymeric tube bundles, the outer wrap configured to tighten the one or more polymeric tube bundles to enable tube configurations to provide uniform spacing between tubes and/or reduce space between the housing and the one or more polymeric tube bundles.
 34. A method of fabricating the one or more polymeric tube bundles of claim 1, the method comprising: forming polymeric tubes by extrusion from a polymer; twisting one or more polymeric tubes to form a twisted tube or a subset of two or more twisted tubes; and forming a bundle of twisted tubes from the twisted tube or the subset of two or more twisted tubes. 